There are many measurement and testing methods which are being used in connection with the manufacturing of gear trains.
For some of these measurement and testing methods two gears are rotated (called engagement rotation) and put in engagement with each other, in order to be able to determine, for instance, how well these two gears can be paired with each other. In this way, the optimum mounting position can be determined.
In order to be able to carry out such measurement and testing methods on spiral gears, typically, in addition to the engagement rotation one or more relative displacement movements (herein called additional movements) are being applied.
The carrying out of such measurement and testing methods on spiral gears thus requires a special machine construction with corresponding axis. Such a machine is herein generally called testing machine or briefly tester. In FIG. 1 an exemplary tester 10 is shown in a very schematic form. A suitable tester 10 has a first spindle 11 for receiving a crown gear T, wherein the crown gear T in a chucked state is mounted so that it can be rotated about the gear axle TA. Furthermore, there is a second spindle 12 which is designed for receiving a pinion R. The second spindle 12 facilitates the rotation of the pinion R about the pinion axle RA.
The corresponding testers 10 comprise a total of five degrees of freedom in order to enable the engagement rotations and the mentioned additional movements between the pinion R and the crown gear T. Altogether, there are five axis provided here, namely two rotational axis TA, RA for the engagement rotation (in case of a tester 10 these are equipped with corresponding sensors, e.g. angular encoders) and three linear axis LA1, LA2, LA3.
The tester 10 enables a relative movement LA1 in the direction of the crown gear axle TA and a relative movement LA2 in the direction of the pinion axle RA. Typically, the distance (parallel to LA3) between the crown gear axle TA and the pinion axle RA can be adjusted in addition, which is referred to as third degree of freedom. The respective linear displacements are also used in order to adjust the mounting distance.
In addition to the mentioned testing machines 10 there are also lapping machines 20 which have a comparable axis constellation with five degrees of freedom. Lapping is a method which is used for the final processing (finishing processing after the quenching) of the tooth flanks of bevel gear pairs (bevel gear trains). After a crown gear T was mounted on a first spindle 21 and a pinion R, which is to be paired therewith, was mounted on a second spindle 22, typically the pinion R is caused to rotate while the crown gear T being engaged with the pinion R runs along or is slowed down. A lapping fluid (e.g. an oil with silicon carbide) is employed as grinding means while the two wheels R and L are carrying out a continuous engagement rotation. During the lapping, the additional movement(s) is/are being carried out in order to extend the lapping action to the total tooth flank surface of the two wheels T and R.
The relative movements of the two exemplary machines 10 and 20 of FIGS. 1 and 2 are identical. But the constellation and assignment of the individual linear axles LA1 through LA3 has been chosen differently in these examples.
Machines are being offered by the producers of lapping machines which differ from each other essentially by differently designed additional movements. Most lapping machines are able to carry out three linear movements, whereby the two horizontal movements LA1, LA2 are a must, since otherwise a shifting of the pinion R would quickly use up the backlash and thus result in a clamping, if the crown gear T would not be moved alongside correspondingly. A vertical axis LA3 is required for the lapping of hypoid gears in order to adjust the axial offset and it can of course be used to displace the bearing pattern during the lapping.
Those machines which are to be automatically fed, at least one of the linear axles (e.g. the linear axle LA2 in FIG. 2) has to have a long displacement range in order to be able to remove the pinion R first and then the crown gear T. For removing the gears R and T a sufficiently large distance between the gears R and T is to be provided.
In order to be able to guarantee high precisions and stiffness, the linear axles of such testers 10 and lapping machines 20 have to be implemented constructively complex and precisely. This results in technically complex and expensive machines.